1. Field of the Invention
The present invention relates to a diamond shape or proportion having a crown or bezel and a pavilion converging up and down from its girdle respectively and a diamond cutting method.
2. Related Arts
A fifty-eight sided diamond shape is well known, and is called round brilliant-cut diamond. One example of such brilliant-cut diamond is shown in Japanese Patent 09-011105(A), claiming a new girdle shape of such a brilliant-cut diamond for patent.
It is absolutely necessary that a fifty-eight sided diamond shape has an octagonal table formed on its crown top. The regular octagonal shape can be determined by drawing a first reference line passing through the center of a circle to halve the circle; drawing a second reference line perpendicular to the first reference line to quadrisect the circle; drawing two intervenient lines at the angle of 45 degrees relative to each of the crossing first and second reference lines; and drawing straight lines to connect adjacent intersections of each divisional line and the circle.
The diamond shape has a thirty-three sided crown cut on its upper part. It is composed of star facets, upper-main facets or bezel facets and upper girdle facets.
Also, the diamond shape has a twenty-five sided pavilion cut on its lower part. It is composed of lower-girdle facets and lower-main facets, which are formed in the sectors delimited by the keel lines running in alignment with the divisional lines of the octagonal table. The pavilion has a culet formed on its bottom center.
The height of the brilliant-cut diamond is approximately 60.4% of the diameter of the girdle; the diameter of the table-tangential circle is approximately 55%; the height of the crown is approximately 15.4%; and the height of the pavilion is approximately 43%. This ratio is the standard proportion of A. G. S. The oblique angle of the crown is 34 degrees whereas that of the pavilion is 41 degrees.
According to the standard of G. I. A. or S. D. N. the height of the brilliant-cut diamond is approximately 59.2 to 60.4% of the diameter of the girdle; the diameter of the table-tangential circle is approximately 53 to 57.5%; the height of the crown is approximately 14.6 to 19%; and the height of the pavilion is approximately 40 to 43.1%. The oblique angle of the crown is 34.xc2xd to 40.06 degrees whereas that of the pavilion is 38.40 to 40.xc2xe degrees.
Every forty-eight sided diamond which meets such standards shines blue although its brightness may be different more or less.
As is described above, a fifty-eight sided diamond piece can be formed by dividing the table-tangential circle by an integer multiple of two to determine the angle of the regular polygon and by determining other dimensions accordingly, and the resultant diamond piece shines in a relatively narrow range of color from yellow to blue.
The highest quality of fifty-eight sided diamond piece shines purple. Other high quality of diamond pieces causes a variety of prism-like effects by different ways of cutting. This suggests that new cutting other than the brilliant-cut can increase the value of jewel significantly.
One object of the present invention is to provide a diamond cutting method that can provide diamond pieces capable of multi-color shining at an increased brightness.
Another object of the present invention is to provide a diamond shape or proportion capable of multi-color shining at an increased brightness.
To attain these objects a diamond cutting method according to the present invention comprises the steps of:
preparing a piece of diamond having a crown or bezel and a pavilion converging up and down from its girdle respectively;
cutting the table of the crown into a regular polygon, which is formed by: drawing reference lines diverging radially from the center of the table, leaving between adjacent reference lines an angular distance equal to the angle determined by dividing 360 degrees by an integer multiple of three; drawing a first table-tangential circle whose diameter is equal to approximately 50 to 53% of the diameter of the girdle; and drawing straight lines between adjacent intersections of the first table-tangential circle and adjacent reference lines;
forming star facets each defined by straight lines drawn from adjacent angles of the regular polygon to a selected intersection of an intervenient bisector drawn between adjacent reference lines and a second circle drawn between the first table-tangential circle and the outermost girdle-tangential circle; and
forming upper-main facets each defined by straight lines drawn from each intersection of each bisector and the second circle to each intersection of each reference line and the outermost girdle-tangential circle, and at the same time, forming paired upper-girdle facets each defined between each upper-main facet and the outermost girdle-tangential circle.
The height of the diamond piece may be approximately 64% of the diameter of the girdle; the height of the crown may be approximately 15.7%; the height of the pavilion may be approximately 48.3%; and the largest width of the girdle may be approximately 1.2 to 1.4%.
The angle formed between the ridge of the crown and the ridge of the pavilion may be approximately 77 degrees.
The shape or proportion of a diamond piece having a crown or bezel and a pavilion converging up and down from its girdle respectively, is so defined according to the present invention that:
the whole height of the diamond piece is approximately 64% of the diameter of the girdle;
the height of the crown is approximately 15.7%;
the height of the pavilion is approximately 48.3%;
the largest width of the girdle is approximately 1.2 to 1.4%;
the diameter of the tangential circle of the polygonal table is 50 to 53%, the regular polygonal shape having sides equal to the integer multiple of three;
the crown has star facets, upper-main facets and upper-girdle facets formed thereon whereas the pavilion has lower-girdle facets and lower-main facets formed on its converging surface, each lower-main facet being partly sandwiched between adjacent lower main facets in each of the sectors, which are delimited by the keel lines extending from the intersections of the bisectors each extending between adjacent reference lines passing through the apexes of the polygonal table and the girdle-tangential circle to the bottom center of the pavilion, at which bottom center the culet is formed, the lower-main facets converging to the culet.
The polygonal table, the star facets, the upper-main facets and the upper-girdle facets together may form a 37- or 49-sided crown whereas the lower-girdle facets, the lower-main facets and the culet together may form a 28- or 37-sided pavilion, thus providing a 65- or 86-sided diamond piece.
The angle formed between the ridge of the crown and the ridge of the pavilion may be approximately 77 degrees.